Abstract:

Chain-extended nanonylon is made from the reaction of oligomeric nanonylon
and chain-extending agents. Such chain-extended nanonylon contains
concentrations of organoclay exceeding 10 weight percent. High
concentrations of organoclay permit the chain-extended nanonylon to be
used as either a concentrate or a compound that provides good barrier
properties for thermoplastic articles made from the chain-extended
nanonylon.

Claims:

1. A process for converting oligomeric nanonylon into chain-extended
nanonylon, comprising the step of reacting the oligomeric nanonylon,
having an organoclay concentration of greater than 10 percent, with a
chain extending agent, selected from the group consisting of
carbodiimides, carbodiimide hydrochlorides, multi-functional epoxies,
carbonylbiscaprolactames, multi-functional acrylic oligomers, and
combinations thereof, to form the chain-extended nanonylon.

9. The process of claim 1, wherein after the reacting step, further
comprising the step of reacting an endcapping agent with the
chain-extended nanonylon, wherein the endcapping agent is selected from
the group consisting of acetic anhydride, phthalic anhydride, hexamethyl
disilazane, acetic acid, and cyclohexylamine.

10. The process of claim 1, wherein the oligomeric nanonylon is present in
an amount ranging from about 10 to about 99.5 weight percent and the
chain extending agent is present in an amount ranging from about 0.5 to
about 20 weight percent.

11. A chain-extended nanonylon have a concentration of organoclay
exceeding 10 percent by weight of the chain-extended nanonylon, wherein
the chain-extended nanonylon is the reaction product of an oligomeric
nanonylon and a chain extending agent selected from the group consisting
of carbodiimides, carbodiimide hydrochlorides, multi-functional epoxies,
carbonylbiscaprolactames, multi-functional acrylic oligomers, and
combinations thereof.

15. The nanonylon of claim 11, wherein the nanonylon is endcapped with am
endcapping agent selected from the group consisting of acetic anhydride,
phthalic anhydride, hexamethyl disilazane, acetic acid, and
cyclohexylamine.

16. The nanonylon of claim 11, wherein chain-extended nanonylon comprises
oligomeric nanonylon present in an amount ranging from about 10 to about
99.5 weight percent and the chain extending agent present in an amount
ranging from about 0.5 to about 20 weight percent.

17. A method of using the chain-extended nanonylon of claim 11, comprising
the step of extruding or molding the chain-extended nanonylon into a
thermoplastic article.

[0002]This invention concerns composites of polyamide and organoclay which
contain concentrations of organoclay in excess of ten weight percent.

BACKGROUND OF THE INVENTION

[0003]The mixture of organoclays and polyamides, commonly called
nanonylons, is highly desired because the organoclays can contribute
barrier properties to polyamides for food packaging and other situations
where the contained product within packaging must not leach, escape, or
decay. Polyamides have been useful since the mid-20th Century.
Organoclays, nanoclays intercalated with organic ions, such as quaternary
ammonium, have become useful in the last decade.

[0004]Presently, nanonylons can be made using two conventional processes:
(1) melt mixing of the organoclay into the previously polymerized nylon,
in which the clay is added to a nylon melt by mechanical action; and (2)
in-situ polymerization of the nylon in the presence of the organoclay, in
which a batch of monomer such as caprolactam is brought to polymerization
in a vessel also containing organoclay.

[0005]An example of melt mixing is found in U.S. Pat. No. 6,605,655 (Kato
et al.). An example of in-situ polymerization is found in U.S. Pat. No.
4,739,007 (Okada et al.).

SUMMARY OF THE INVENTION

[0006]Unfortunately, there are difficulties with both preparation methods
for nanonylons.

[0007]Melt mixing of organoclay with pre-polymerized nylon fails to
achieve the extent of dispersion required for establishing the full
benefits of the organoclay throughout the bulk of the nylon, which fails
to approach optimized barrier properties for nanonylon films, containers
and other articles in which limitation of transport through the nanonylon
is highly desired. Moreover, melt mixing with too high a concentration of
organoclay can create viscosity problems in the mixing device.

[0008]In-situ polymerization of nylon from monomer in the presence of
organoclay ("polymerized nanonylon") currently has a practical limit of
about 8% concentration by weight of the organoclay in the nanonylon,
above that concentration the polymerized nylon containing the organoclay
is often too viscous for convenient removal from the reaction chamber.
Therefore, while an 8% nanonylon may be suitable for a nanonylon
compound, it is not suitable for a nanonylon concentrate, an intermediate
product which is sold to customers to extrude or mold with a "let-down"
dilution of the concentrate in the presence of additional nylon, other
polymers, other compounding ingredients, and the like.

[0009]Thus, the problem in the art is that nanonylon presently has a
practical concentration limit of about 8%, while there are many who
desire a concentration of organoclay in a concentrate that exceeds well
beyond 8%.

[0010]The present invention solves this problem by using chain extension
chemistry in a reactive extrusion process.

[0011]More precisely, the present invention begins with a preliminary low
molecular weight nanonylon to make a final high molecular weight
nanonylon.

[0012]The preliminary nanonylon is a mixture of organoclay with nylon
having a low molecular weight. Thus, the starting material for the
process of the present invention is a polymerized nanonylon of low
molecular weight, sometimes also called an "oligomer". For purposes of
this invention, the starting material will be called "oligomeric
nanonylon".

[0013]Oligomeric nanonylon is commercially available because it can be
prepared without encountering the viscosity problems encountered by the
preparation of "polymerized nanonylon". Because the polymerization
reaction of monomer-s, such as caprolactam, is halted before the
molecular weight of the nylon becomes excessive, in terms of viscosity,
the oligomeric nanonylon can be prepared in a batch reactor without
reaching the limit of viscosity to impede the removal of the reacted
product, also called a "drop" of the polymerized nylon.

[0014]With conventional chain extension agents, the present invention
takes oligomeric nanonylon and extends the chains of nylon, making a
nylon with higher molecular weight, higher melt flow index, greater
viscosity, etc. while retaining essentially the same amount of the higher
concentration of organoclay therewithin in a condition as dispersed as
the organoclay has been in the oligomeric nanonylon. For purposes of this
invention, to distinguish the product of this invention from "polymerized
nanonylon", the product of this invention will be called "chain-extended
nanonylon".

[0015]Thus, one aspect of this invention is a process for converting
oligomeric nanonylon into chain-extended nanonylon. That process uses a
continuous reaction vessel such as an extruder in which the dwell time of
the oligomeric nanonylon is sufficient to complete chain extension to a
desired level, thus forming a chain-extended nanonylon which can be used
for subsequent dilution into a thermoplastic compound or be used as a
compound itself for situations where a very high concentration of
organoclay is desired in the final molded or extruded article.

[0016]Another aspect of the present invention is the chain-extended
nanonylon formed by the process of the present invention. Irrespective of
how this chain-extended nanonylon has been made, because of the viscosity
and dispersion problems with conventional methods of making polymerized
nanonylon, it is believed that a new product has been invented: a
nanonylon having an organoclay concentration exceeding 10 weight percent,
desirably exceeding 25 weight percent, and preferably exceeding 35 weight
percent, a multi-fold increase in organoclay concentration not previously
commercially available as an intermediate product (concentrate) or as a
final product (compound) in the field of nanonylon composites.

[0017]A third aspect of the present invention is the use of chain-extended
nanonylon in the manufacture of a thermoplastic compound, suitable for
extruding or molding into a variety of article forms, such as films,
fibers, vessels, etc.

[0018]A fourth aspect of the present invention is the article made from
the chain-extended nanonylon.

[0019]Features and advantages of the invention will be explained below
while discussing the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is plot of complex viscosity relative to angular frequency
for Comparative Example A and Examples 1-7.

[0023]The chain-extended nano nylon is dependent on the content and
properties of the oligomeric nanonylon. Briefly stated, it is known that
an oligomeric nanonylon containing as much as 20 weight percent of
organoclay is commercially available by or through Nanocor, Inc. of
Arlington Heights, Ill., USA. It has been measured that the 20 weight
percent organoclay has a melt flow index of about 73 g/10 min. @
235° C. and 1.4.9 Kg of force. Nanocor, Inc. is a world leader in
the manufacture and sale of organoclays and organoclay concentrates.

[0024]As technology advances to create oligomeric nanonylons with
organoclay concentrations exceeding even 20 weight percent, this
invention will be just as suitable for such new oligomeric nanonylons.

[0025]To achieve a 20 weight percent oligomeric nanonylon, an in-situ
polymerization of caprolactam (cyclic compounds represented, which
undergo ring-opening polymerization to form polyamides), can be used to
intercalate the nanoclay with polyamide polymerized from caprolactam,
according to the teachings of U.S. Pat. No. 4,739,007, but with the
altered step of stopping the reaction before the polymerized monomer
grows beyond oligomeric level.

[0026]The oligomeric nanonylon used in the present invention should have a
weight average molecular weight of nylon, ranging from about 10,000 to
about 50,0000, and preferably from about 25,000 to about 35,000.

[0027]Organoclays

[0028]Organoclays arrive at the cusp of the present invention already as a
part of the oligomeric nanonylon. However, the ability to determine which
organoclay to use, and hence which oligomeric nanonylon to use, will be
possible to a person practicing this invention.

[0029]Organoclay is obtained from nanoclay. Nanoclay is a clay from the
smectite family. Smectites have a unique morphology, featuring one
dimension in the nanometer range. Montmorillonite clay is the most common
member of the smectite clay family. The montmorillonite clay particle is
often called a platelet, meaning a sheet-like structure where the
dimensions in two directions far exceed the particle's thickness.

[0030]Nanoclay becomes commercially significant if intercalated with an
organic intercalant to become an organoclay. An intercalate is a
clay-chemical complex wherein the clay gallery spacing has increased, due
to the process of surface modification by an intercalant. Under the
proper conditions of temperature and shear, an intercalate is capable of
exfoliating in a resin matrix, such as a polyamide. An intercalant is an
organic or semi-organic chemical capable of entering the montmorillonite
clay gallery and bonding to the surface. Exfoliation describes a
dispersion of an organoclay (surface treated nanoclay) in a plastic
matrix. In this invention, oligomeric nanonylon has exfoliated organoclay
at least to some extent and preferably in excess of that achievable using
the conventional melt mixing, process for making polymerized nanonylons.

[0031]In exfoliated form, nanoclay platelets have a flexible sheet-type
structure which is remarkable for its very small size, especially the
thickness of the sheet. The length and breadth of the particles range
from 1.5 μm down to a few tenths of a micrometer. However, the
thickness is astoundingly small, measuring only about a nanometer (a
billionth of a meter). These dimensions result in extremely high average
aspect ratios (200-500). Moreover, the miniscule size and thickness mean
that a single gram contains over a million individual particles.

[0032]Nanocomposites are the combination of the organoclay and the plastic
matrix. In polymer compounding, a nanocomposite is a very convenient
means of delivery of the nanoclay into the ultimate compound, provided
that the plastic matrix is compatible with the principal polymer resin
components of the compounds. In such manner, nanocomposites are available
in concentrates, masterbatches, and compounds from Nanocor, Inc. of
Arlington Heights, Ill. (wwvw.nanocor.com) and PolyOne Corporation of
Avon Lake, Ohio (www.polyone.com) in a variety of nanocomposites.
Particularly preferred organoclays are I24P, I30P, and I44P from Nanocor,
Inc.

[0033]With respect to oligomeric nanonylons, as explained above, Nanocor
has commercially available an oligomeric nanonylon meeting the
specifications of molecular weight, melt flow index, or viscosity as
identified above for use in this invention. Other commercial sources are
likely to become available as the technology emerges.

[0034]Nanocomposites offer flame-retardancy properties because such
nanocomposite formulations burn at a noticeably reduced burning rate and
a hard char forms on the surface. They also exhibit minimum dripping and
fire sparkling.

[0035]Moreover, nanocomposites made from nylon as the thermoplastic matrix
also have barrier properties useful in films, fibers, and other forms.
Barrier properties can be measured as transmission rates, namely for
oxygen transmission rates in the units of cc-mil/100 in2-day and for
water vapor transmission rates, g-mil/m2-day, respectively.
Chain-extended nanonylons made according to the present invention can
have oxygen transmission rates ranging from about 2.3 to about 0.5, and
preferably from about 0.8 to about 0.5 cc-mil/100 in2-day, when
measured at 65% relative humidity. Chain-extended nanonylons made
according to the present invention can have water vapor transmission
rates ranging from about 325 to about 25, and preferably from about 30 to
about 25 g-mil/m2-day.

[0036]Nylons

[0037]The polyamides useful for making the oligomeric nanonylon can be one
or a number of polyamides, (nylons) comprise crystalline or resinous,
high molecular weight solid polymers including copolymers and terpolymers
having recurring amide units within the polymer chain. Polyamides may be
prepared in the presence of organoclays by polymerization, only to an
oligomeric level, of one or more epsilon lactams such as caprolactam,
pyrrolidone, lauryllactam and aminoundecanoic lactam, or amino acid, or
by condensation of dibasic acids and diamines.

[0044]The chain-extended nanonylon of the present invention can include
conventional plastics additives in an amount that is sufficient to obtain
a desired processing or performance property for the ultimate
thermoplastic compound, but in a manner that does not disrupt the
reaction chain extending agents with the oligomeric nanonylon to form the
chain-extended nanonylon.

[0045]The amount should not be wasteful of the additive nor detrimental to
the processing or performance of the compound. Those skilled in the art
of thermoplastics compounding, without undue experimentation but with
reference to such treatises as Plastics Additives Database (2004) from
Plastics Design Library (www.williamandrew.com), can select from many
different types of additives for inclusion into the chain-extended
nanonylons of the present invention.

[0048]While the chain-extended nanonylon can be made without other
polymers present, it is optional to introduce other polymers into the
extruder for a variety of ultimate compound properties and performances,
but in a manner that does not disrupt the reaction chain extending agents
with the oligomeric nanonylon to form the chain-extended nanonylon.

[0049]The same polyamide as constitutes the nanonylon can be added if it
is desired to dilute the organoclay concentration in the nylon to a
specific lower level. Likewise, a blend of thermoplastics can be created
at this time of chain extension reaction by using other polyamides or
other resins such as those selected from the group consisting of
polyolefins, polyimides, polycarbonates, polyesters, polysulfones,
polylactones, polyacetals, acrylonitrile-butadiene-styrene resins (ABS),
polyphenyleneoxide (PPO), polyphenylene sulfide (PPS), polystyrene,
styrene-acrylonitrile resins (SAN), styrene maleic anhydride resins
(SMA), aromatic polyketones (PEEK, PED, and PEKK) and mixtures thereof.
Also, any polymer that is reactive with the chain extending agent(s) can
be added into the extruder to form copolymers with the polyamide during
reactive extrusion, in order to form a chain-extended copolymeric
nanonylon.

[0050]Optional Endcapping Agents

[0051]Because chain extension begins with reaction at functional groups at
the ends of the nylon oligomer, after reaction with the chain extending
agents, it is optional to introduce endcapping agents to the extruder to
forestall any addition reaction of the ends of the chain-extended
nanonylon beyond the desired molecular weight, desired melt flow index,
or desired viscosity.

[0053]Table 1 shows ranges of acceptable, desirable, and preferred weight
percents of the various ingredients for addition to the extruder,
relative to the total weight of the chain-extended nanonylon emerging
from the extruder, all being expressed as approximate values. Because the
additives, other polymers, and endcapping agents are optional, the low
end of each range is zero.

[0055]The preparation of compounds of the present invention is
uncomplicated. The compound of the present can be made in batch or
continuous operations.

[0056]Reaction via chain extension in a continuous process for this
invention occurs in an extruder that is elevated to a temperature that is
sufficient to melt the oligomeric nanonylon and to adequate disperse the
chain extending agent and optional additive and optional polymers
therewithin.

[0057]Extruders have a variety of screw configurations, including but not
limited to single and double, and within double, co-rotating and
counter-rotating. Extruders also include kneaders and continuous mixers,
both of which use screw configurations suitable for mixing by those
skilled in the art without undue experimentation. In the present
invention, it is preferred for chain extension to use a twin co-rotating
screw in an extruder commercially available from Coperion
Werner-Pfleiderer GmbH of Stuttgart, Germany.

[0058]Extruders have a variety of heating zones and other processing
parameters that interact with the elements of the screw(s). Extruders can
have temperatures and other conditions according to acceptable,
desirable, and preferable ranges as shown in Table 2.

[0059]Location of ingredient addition into the extruder can be varied
according the desired duration of dwell time in the extruder for the
particular ingredient. Table 3 shows acceptable, desirable, and
preferable zones when ingredients are to be added in the process of the
present invention.

[0060]Extruder speeds can range from about 50 to about 1200 revolutions
per minute (rpm), and preferably from about 300 to about 600 rpm.

[0061]Typically, the output from the extruder is pelletized for later
extrusion or molding into polymeric articles.

[0062]The chair-extended nanonylon of the present invention should have a
weight average molecular weight of nylon, ranging from about 15,000 to
about 80,000, and preferably from about 30,000 to about 60,000. Thus, the
weight average molecular weight of the chain-extended nanonylon can be as
much as 8-fold the starting weight average molecular weight of the
oligomeric nanonylon.

[0063]Subsequent Processing

[0064]The chain-extended nanonylon made according to the present invention
can serve either as a concentrate or as a compound. If the former, then
the chain-extended nanonylon is an intermediate product, an ingredient to
be added with other ingredients to subsequent compounding steps in a
batch or continuous mixing apparatus. The dilution or "let-down" of the
concentrate into the compound can result in an organoclay concentration
in the compound ranging from about 0.5 to about 10 weight percent, and
preferably from about 3 to about 8 weight percent.

[0065]Ultimately, the compound is formed into an article using a
subsequent extrusion or molding techniques. These techniques are well
known to those skilled in the art of thermoplastics polymer engineering.
Without undue experimentation but using references such as "Extrusion,
The Definitive Processing Guide and Handbook"; "Handbook of Molded Part
Shrinkage and Warpage"; "Specialized Molding Techniques"; "Rotational
Molding Technology"; and "Handbook of Mold, Tool and Die Repair Welding",
all published by Plastics Design Library (www.william-andrew.com), one
can make articles of any conceivable shape and appearance using
chain-extended nanonylons of the present invention.

Usefulness of the Invention

[0066]Chain-extended nanonylons of the present invention are useful for
making packaging film; closures; containers of all shapes; impact
modified articles; transportation-related molded items (e.g., crash
helmets and parts for vehicles such as bumpers and fenders); electrical
equipment when flame retardants or reinforcing fillers are also added
(e.g., plugs, connectors, boxes, and switches); and consumer appliance
housings and containers (e.g., kitchen appliance housings and shells, and
consumer electronics housings and cases).

[0067]Further embodiments of the invention are described in the following
Examples.

[0069]For purposes of this invention, experimentations with 8% nanonylon
are asserted to be establishment of efficacy of the inventive process to
chain-extend a nanonylon. This efficacy experiment predicted the results
for nanonylon of greater concentrations of organoclay (e.g., about 20%)
because of the same chemistry shared by polymerized nanonylon of 8%
organoclay concentration and oligomeric nanonylon of 20% organoclay
concentration in respect of the reactivity of the nylon ends to the chain
extending agents. Table 4 shows the formulations of the eight samples,
divided between lettered Comparative Examples and numerical Examples.

[0070]All 8 samples were made on a 16 mm Prism co-rotating twin screw
extruder made by Thermo Electron Corporation of Stone, U.K. All
ingredients were added at the throat. The feeder rate was 7% for
Comparative Example A and Examples 4-7 and 6% for Examples 1-3. The
temperatures were set at 230° C. for Zones 1-5, 240° C. for
Zones 6 and 7, 250° C. for Zones 8 and 9, and 260° C. for
the die.

[0072]FIG. 1 and the data show the complex log-viscosity of the control 8%
Nanonylon (Comparative Example A) and the various Examples 1-7. Bruggolen
M1251 (Examples 1-3) increased complex log-viscosity at high angular
frequencies approximately proportional to loading level. The effect was
convergent at low angular frequency and was similar to Comparative
Example A at low angular frequencies.

[0074]Raschig 9000 (Examples 6 and 7) produced the largest increase in
complex log-viscosity at both loading levels. The increase in viscosity
was about a half decade at a loading level of 1.5% and slightly higher at
2.5% loading level.

[0075]FIG. 2 shows the Cole-Cole plots of the frequency-dependent loss and
storage moduli of Comparative Example A and Examples 1-7, using the data
from Table 5. Cole-Cole plots are explained in Harrell et al., "Modified
Cole-Cole Plot Based on Viscoelastic Properties for Characterizing
Molecular Architecture of Elastomers" Journal of Applied Polymer Science,
Vol. 29, 995-1010 (1984).

[0076]Bruggolen M1251 (Examples 1-3) at all loading levels did not
significantly shift the curves toward the G''=G' line to indicate long
chain branching. Nevertheless, at low shear storage modulus, G', (or
short relaxation times), there was a change in curvature towards the
G''=G' line, which indicated time/frequency-dependent structural changes.
However, there was an increase in complex log-viscosity. Therefore, this
indicated an increase in chain extension, as evidenced by an increase
complex-log viscosity. There was no evidence of long chain branching, but
some time/frequency-dependent structural changes.

[0077]Raschig 7000 (Examples 4 and 5), similar to Bruggolen M1251
(Examples 1-3), showed no long chain branching, but there was evidence of
structural changes. From the complex log-viscosity curves, there was only
a moderate increase, which was attributable mainly to chain extension.

[0078]Raschig 9000 (Examples 6 and 7) shifted closer to the G''=G' line
with increasing loading levels indicating structural changes associated
with long chain branching. At a loading level of 1.5%, there was also
some evidence of structural changes, was believed to have arisen from an
effect of Raschig 9000 on the nylon-organoclay interaction on branching.
That effect was also apparent at a loading level of 2.5%. From the
complex log-viscosity curves and the Cole-Cole plots, Raschig 9000
appears to have the greatest amount of chain extension as well as long
chain branching, which assists in articles that require good melt
strength, such as foamed articles, blow-molded articles, thermoformed
articles, calendered articles, and fiberformed articles.

[0079]From the Complex modulus, G* versus angular frequency plots, the
molecular weight shift factor, alpha or α, was calculated for all
samples. The shift factor corresponded to the amount of shift required to
superpose the G* versus angular frequency curves onto a reference curve
(control) in order to form a master curve. From the shift factors
obtained, the molecular weights relative to the control sample were
obtained.